Ken,
I could never find N.O.S. end bumper bolts. My originals self-destructed when I took my bumpers off. I ended up using ones I found at Restoration Specialties that were for either a 1937 or a 1939 DeSoto. Don’t know the part number, I lost the receipt for it. They have an oval shaped head that is a little longer than the original but has the same contour to fit around the rounded bumper end.

Also, I got my horns working again by energizing them with a battery and tapping on them with a rubber mallet. Eventually they started blowing again.